Life-threatening arrhythmias with autosomal recessive TECRL variants.

AIMS: Sudden death and aborted sudden death have been observed in patients with biallelic variants in TECRL. However, phenotypes have only begun to be described and no data are available on medical therapy after long-term follow-up. METHODS AND RESULTS: An international, multi-centre retrospective review was conducted. We report new cases associated with TECRL variants and long-term follow-up from previously published cases. We present 10 cases and 37 asymptomatic heterozygous carriers. Median age at onset of cardiac symptoms was 8 years (range 1-22 years) and cases were followed for an average of 10.3 years (standard deviation 8.3), right censored by death in three cases. All patients on metoprolol, bisoprolol, or atenolol were transitioned to nadolol or propranolol due to failure of therapy. Phenotypes typical of both long QT syndrome and catecholaminergic polymorphic ventricular tachycardia (CPVT) were observed. We also observed divergent phenotypes in some cases despite identical homozygous variants. None of 37 heterozygous family members had a cardiac phenotype. CONCLUSION: Patients with biallelic pathogenic TECRL variants present with variable cardiac arrhythmia phenotypes, including those typical of long QT syndrome and CPVT. Nadolol and propranolol may be superior beta-blockers in this setting. No cardiac disease or sudden death was present in patients with a heterozygous genotype.

Calmodulin mutations and life-threatening cardiac arrhythmias: insights from the International Calmodulinopathy Registry.

AIMS: Calmodulinopathies are rare life-threatening arrhythmia syndromes which affect mostly young individuals and are, caused by mutations in any of the three genes (CALM 1-3) that encode identical calmodulin proteins. We established the International Calmodulinopathy Registry (ICalmR) to understand the natural history, clinical features, and response to therapy of patients with a CALM-mediated arrhythmia syndrome. METHODS AND RESULTS: A dedicated Case Report File was created to collect demographic, clinical, and genetic information. ICalmR has enrolled 74 subjects, with a variant in the CALM1 (n = 36), CALM2 (n = 23), or CALM3 (n = 15) genes. Sixty-four (86.5%) were symptomatic and the 10-year cumulative mortality was 27%. The two prevalent phenotypes are long QT syndrome (LQTS; CALM-LQTS, n = 36, 49%) and catecholaminergic polymorphic ventricular tachycardia (CPVT; CALM-CPVT, n = 21, 28%). CALM-LQTS patients have extremely prolonged QTc intervals (594 ± 73 ms), high prevalence (78%) of life-threatening arrhythmias with median age at onset of 1.5 years [interquartile range (IQR) 0.1-5.5 years] and poor response to therapies. Most electrocardiograms (ECGs) show late onset peaked T waves. All CALM-CPVT patients were symptomatic with median age of onset of 6.0 years (IQR 3.0-8.5 years). Basal ECG frequently shows prominent U waves. Other CALM-related phenotypes are idiopathic ventricular fibrillation (IVF, n = 7), sudden unexplained death (SUD, n = 4), overlapping features of CPVT/LQTS (n = 3), and predominant neurological phenotype (n = 1). Cardiac structural abnormalities and neurological features were present in 18 and 13 patients, respectively. CONCLUSION: Calmodulinopathies are largely characterized by adrenergically-induced life-threatening arrhythmias. Available therapies are disquietingly insufficient, especially in CALM-LQTS. Combination therapy with drugs, sympathectomy, and devices should be considered.

Digenic Inheritance of LAMA4 and MYH7 Mutations in Patient with Infantile Dilated Cardiomyopathy.

Background and objectives: Dilated cardiomyopathy (DCM) is a rare cardiac disease characterised by left ventricular enlargement, reduced left ventricular contractility, and impaired systolic function. Childhood DCM is clinically and genetically heterogenous and associated with mutations in over 100 genes. The aim of this study was to identify novel variations associated with infantile DCM. Materials and Methods: Targeted next generation sequencing (NGS) of 181 cardiomyopathy-related genes was performed in three unrelated consanguineous families from Saudi Arabia. Variants were confirmed and their frequency established in 50 known DCM cases and 80 clinically annotated healthy controls. Results: The three index cases presented between 7 and 10 months of age with severe DCM. In Family A, there was digenic inheritance of two heterozygous variants: a novel variant in LAMA4 (c.3925G > A, p.Asp1309Asn) and a known DCM mutation in MYH7 (c.2770G > A; p.Glu924Lys). The LAMA4 p.Asp1309Asn variant was predicted to be likely pathogenic according to international guidelines. The other two families had no identifiable potentially deleterious variants. Conclusions: Inheritance of two genetic variants may have a synergistic or dose effect to cause severe DCM. We report of a novel p.Asp1309Asn variation associated with DCM. Targeted NGS is useful in the molecular diagnosis of DCM and to guide whole-family management and counselling.

Genotype and clinical characteristics of congenital long QT syndrome in Thailand.

BACKGROUND: Congenital long QT syndrome (LQTS) is an inheritable arrhythmic disorder which is linked to at least 17 genes. The clinical characteristics and genetic mutations may be variable among different population groups and they have not yet been studied in Thai population. METHODS: Clinical characteristics were retrospectively reviewed from children and young adults with congenital long QT syndrome whose blood samples were sent for genotyping during 1998-2017. Sangers sequencing was used to sequentially identify KCNQ1 or KCNH2 genetic variants. Whole exome sequencing (WES) was used to identify variants in all other known LQTS genes. RESULTS: Of the 20 subjects (17 families), 45% were male, mean QTc was 550.3 ±â€¯68.8 msec (range 470-731 msec) and total Schwartz's score was 5.6 ±â€¯1.2 points (range 3-8 points). Fifty percent of patients had events at rest, 30% had symptoms after adrenergic mediated events, and 20% were asymptomatic. We discovered pathogenic and likely pathogenic genetic variants in KCNQ1, KCNH2, and SCN5A in 6 (35%), 4 (24%), and 2 (12%) families, respectively. One additional patient had variance of unknown significance (VUS) in KCNH2 and another one in ANK2. No pathogenic genetic variant was found in 3 patients (18%). Most patients received beta-blocker and 9 (45%) had ICD implanted. LQT1 patients were either asymptomatic or had stress-induced arrhythmia. Most of the LQT2 and LQT3 patients developed symptoms at rest or during sleep. CONCLUSIONS: Our patients with LQTS were mostly symptomatic at presentation. The genetic mutations were predominantly in LQT1, LQT2, and LQT3 genes.

[Multidisciplinary cardiogenetic counselling]. / Consultation multidisciplinaire de cardiogénétique.

Multidisciplinary cardiogenetic consulting offers a global clinical approach to patients suffering from channelopathies or hereditary cardiomyopathies. Mutation is discovered in around 50 % of the cases. Several experts are working together to bring probands and their families useful and necessary informations to help them understanding causes, consequences and support of their disease. This approach is developped in close collaboration with the treating physician.

La consultation multidisciplinaire de cardiogénétique offre une approche globale spécialisée aux patients souffrant de canalopathies ou de cardiomyopathies héréditaires. Une mutation génétique est identifiée dans près de 50 % des cas. Les différents experts engagés travaillent conjointement pour apporter aux patients et à leurs familles les renseignements utiles et nécessaires pour comprendre les causes, les conséquences et la prise en charge de la maladie concernée. La consultation se fait en étroite collaboration avec les médecins traitants.

A Zebrafish Loss-of-Function Model for Human CFAP53 Mutations Reveals Its Specific Role in Laterality Organ Function.

Establishing correct left-right asymmetry during embryonic development is crucial for proper asymmetric positioning of the organs. Congenital heart defects, such as dextrocardia, transposition of the arteries, and inflow or outflow tract malformations, comprise some of the most common birth defects and may be attributed to incorrect establishment of body laterality. Here, we identify new patients with dextrocardia who have mutations in CFAP53, a coiled-coil domain containing protein. To elucidate the mechanism by which CFAP53 regulates embryonic asymmetry, we used genome editing to generate cfap53 zebrafish mutants. Zebrafish cfap53 mutants have specific defects in organ laterality and randomization of asymmetric gene expression. We show that cfap53 is required for cilia rotation specifically in Kupffer's vesicle, the zebrafish laterality organ, providing a mechanism by which patients with CFAP53 mutations develop dextrocardia and heterotaxy, and confirming previous evidence that left-right asymmetry in humans is regulated through cilia-driven fluid flow in a laterality organ.

p.L1612P, a novel voltage-gated sodium channel Nav1.7 mutation inducing a cold sensitive paroxysmal extreme pain disorder.

BACKGROUND: Mutations in the SCN9A gene cause chronic pain and pain insensitivity syndromes. We aimed to study clinical, genetic, and electrophysiological features of paroxysmal extreme pain disorder (PEPD) caused by a novel SCN9A mutation. METHODS: Description of a 4-generation family suffering from PEPD with clinical, genetic and electrophysiological studies including patch clamp experiments assessing response to drug and temperature. RESULTS: The family was clinically comparable to those reported previously with the exception of a favorable effect of cold exposure and a lack of drug efficacy including with carbamazepine, a proposed treatment for PEPD. A novel p.L1612P mutation in the Nav1.7 voltage-gated sodium channel was found in the four affected family members tested. Electrophysiologically the mutation substantially depolarized the steady-state inactivation curve (V1/2 from -61.8 ± 4.5 mV to -30.9 ± 2.2 mV, n = 4 and 7, P < 0.001), significantly increased ramp current (from 1.8% to 3.4%, n = 10 and 12) and shortened recovery from inactivation (from 7.2 ± 5.6 ms to 2.2 ± 1.5 ms, n = 11 and 10). However, there was no persistent current. Cold exposure reduced peak current and prolonged recovery from inactivation in wild-type and mutated channels. Amitriptyline only slightly corrected the steady-state inactivation shift of the mutated channel, which is consistent with the lack of clinical benefit. CONCLUSIONS: The novel p.L1612P Nav1.7 mutation expands the PEPD spectrum with a unique combination of clinical symptoms and electrophysiological properties. Symptoms are partially responsive to temperature but not to drug therapy. In vitro trials of sodium channel blockers or temperature dependence might help predict treatment efficacy in PEPD.

De novo mutation in the KCNQ1 gene causal to Jervell and Lange-Nielsen syndrome.

Jervell and Lange-Nielsen syndrome (JLNS) is an autosomal recessive disorder, clinically characterized by severe cardiac arrhythmias [due to prolonged QTc interval in electrocardiogram (ECG)] and bilateral sensory neural deafness. Molecular defects causal to JLNS are either homozygous or compound heterozygous mutations, predominantly in the KCNQ1 gene and occasionally in the KCNE1 gene. As the molecular defect is bi-allelic, JLNS patients inherit one pathogenic mutation causal to the disorder from each parent. In this report, we show for the first time that such a disorder could also occur due to a spontaneous de novo mutation in the affected individual, not inherited from the parent, which makes this case unique unlike the previously reported JLNS cases.

EMQN: Recommendations for genetic testing in inherited cardiomyopathies and arrhythmias.

Inherited cardiomyopathies and arrhythmias (ICAs) are a prevalent and clinically heterogeneous group of genetic disorders that are associated with increased risk of sudden cardiac death and heart failure. Making a genetic diagnosis can inform the management of patients and their at-risk relatives and, as such, molecular genetic testing is now considered an integral component of the clinical care pathway. However, ICAs are characterised by high genetic and allelic heterogeneity, incomplete / age-related penetrance, and variable expressivity. Therefore, despite our improved understanding of the genetic basis of these conditions, and significant technological advances over the past two decades, identifying and recognising the causative genotype remains challenging. As clinical genetic testing for ICAs becomes more widely available, it is increasingly important for clinical laboratories to consolidate existing knowledge and experience to inform and improve future practice. These recommendations have been compiled to help clinical laboratories navigate the challenges of ICAs and thereby facilitate best practice and consistency in genetic test provision for this group of disorders. General recommendations on internal and external quality control, referral, analysis, result interpretation, and reporting are described. Also included are appendices that provide specific information pertinent to genetic testing for hypertrophic, dilated, and arrhythmogenic right ventricular cardiomyopathies, long QT syndrome, Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia.

Identification of a de novo LRP1 mutation in a Saudi family with Tetralogy of Fallot.

BACKGROUND: Tetralogy of Fallot (TOF) is a rare, complex congenital heart defect caused by genetic and environmental interactions that results in abnormal heart development during the early stages of pregnancy. Genetic basis of TOF in Saudi populations is not yet studied. Therefore, the objective of this study is to screen for the molecular defects causing TOF in Saudi patients. METHODS: A family with non-syndromic TOF was recruited from the Western region of Saudi Arabia. Whole exome sequencing (WES) was performed on the proband and her parents. The identified candidate variant was verified by sanger sequencing. Also, different computational biology tools were used to figure out how candidate variants affect the structure and function of candidate protein involved in TOF. RESULTS: A novel heterozygous de novo mutation in LRP1 (p. G3311D) gene was identified in the index case. Also, this variant was absent in the in-house exome sequencing data of 80 healthy Saudi individuals. This variant was predicted to be likely pathogenic, as it negatively affects the biophysical chemical properties and stability of the protein. Furthermore, functional biology data from knock out mouse models confirms that molecular defects in LRP1 gene leads to cardiac defects and lethality. This variant was not previously reported in both Arab and global population genetic databases. CONCLUSION: The findings in this study postulate that the LRP1 variant has a role in TOF pathogenesis and facilitate accurate diagnosis as well as the understanding of underlying molecular mechanisms and pathophysiology of the disease.

SCN5A overlap syndromes: An open-minded approach.

SCN5A overlap syndromes are clinical entities that express a phenotype combining aspects of different canonical SCN5A-related arrhythmia syndromes or a variable arrhythmic phenotype among individuals carrying the same SCN5A mutation. Here we review the literature addressing SCN5A overlap syndromes as well as the principal mechanisms currently proposed. Among others, a multifactorial determination encompassing an interaction between SCN5A variant(s), other genetic polymorphisms, and possibly environmental factors seems the most plausible hypothesis.

Left cardiac sympathetic denervation for catecholaminergic polymorphic ventricular tachycardia.

Catecholaminergic polymorphic ventricular tachycardia is a potentially lethal disease characterized by adrenergically mediated ventricular arrhythmias manifested especially in children and teenagers. Beta-blockers are the cornerstone of therapy, but some patients do not have a complete response to this therapy and receive an implantable cardioverter-defibrillator (ICD). Given the nature of catecholaminergic polymorphic ventricular tachycardia, ICD shocks may trigger new arrhythmias, leading to the administration of multiple shocks. We describe the long-term efficacy of surgical left cardiac sympathetic denervation in three young adults with catecholaminergic polymorphic ventricular tachycardia, all of whom had symptoms before the procedure and were symptom-free afterward.

An intronic mutation leading to incomplete skipping of exon-2 in KCNQ1 rescues hearing in Jervell and Lange-Nielsen syndrome.

Romano-Ward syndrome (RWs) and Jervell and Lange-Nielsen Syndrome (JLNs) are two inherited arrhythmia disorders caused by monoallelic or bi-allelic mutations, respectively, in the KCNQ1 or KCNE1 genes. Both disorders could cause Long QT syndrome either without deafness (RWs), or with deafness (JLNs). We have performed clinical, molecular and functional investigation in two consanguineous Arabian families with history of sudden death of several children. Importantly, none of the affected individuals had (or have) any hearing impairment. Homozygosity mapping followed by molecular analysis identified a novel splice acceptor site mutation (homozygously) in intron-1 of the KCNQ1 gene (c.387 -5T>A), in these two apparently unlinked families. RNA analysis revealed that this splice site mutation causes incomplete transcriptional aberration of the KCNQ1 gene, leaving 10% of the normal allele transcript intact, which restores the hearing function. Our molecular and functional data provide the first evidence that small amount (as low as 10%) of normal KCNQ1 current can effectively maintain the hearing function but fails to maintain cardiac repolarization characteristics within normal limits. Additionally, we have revealed four extra low frequency aberrant isoforms emphasizing the importance of intronic and other non-coding sequences in maintaining cellular homeostasis as pathologic changes in a single nucleotide can affect splicing events at distant sites. The novel KCNQ1 mutation found in this study is very likely a founder mutation in the southern province of Saudi Arabia emphasizing its screening in the LQT population in this region.

Clinical and genetic analysis of long QT syndrome in children from six families in Saudi Arabia: are they different?

Congenital long QT syndrome (LQTS) is an inherited cardiac arrhythmia disorder characterized by prolongation of the QT interval; patients are predisposed to ventricular tachyarrhythmias and fibrillation leading to recurrent syncope or sudden cardiac death. We performed clinical and genetic studies in six Saudi Arabian families with a history of sudden unexplained death of children. Clinical symptoms, ECG phenotypes, and genetic findings led to the diagnosis of LQT1 in two families (recessive) and LQT2 in four families (three recessive and one dominant). Onset of arrhythmia was more severe in the recessive carriers and occurred during early childhood in all recessive LQT1 patients. Arrhythmia originated at the intrauterine stages of life in the recessive LQT2 patients. LQT1, causing mutation c.387-5 T > A in the KCNQ1 gene, and LQT2, causing mutation c.3208 C > T in the KCNH2 gene, are presumably founder mutations in the Assir province of Saudi Arabia. Further, all LQTS causing mutations detected in this study are novel and have not been reported in other populations.

Dihydropyrimidine Dehydrogenase Deficiency: Homozygosity for an Extremely Rare Variant in DPYD due to Uniparental Isodisomy of Chromosome 1.

Dihydropyrimidine dehydrogenase (DPD) deficiency is a rare autosomal recessive disorder of the pyrimidine degradation pathway and can lead to intellectual disability, motor retardation, and seizures. Genetic variations in DPYD have also emerged as predictive risk factors for severe toxicity in cancer patients treated with fluoropyrimidines. We recently observed a child born to non-consanguineous parents, who demonstrated seizures, cognitive impairment, language delay, and MRI abnormalities and was found to have marked thymine-uraciluria. No residual DPD activity could be detected in peripheral blood mononuclear cells. Molecular analysis showed that the child was homozygous for the very rare c.257C > T (p.Pro86Leu) variant in DPYD. Functional analysis of the recombinantly expressed DPD mutant showed that the DPD mutant carrying the p.Pro86Leu did not possess any residual DPD activity. Carrier testing in parents revealed that the father was heterozygous for the variant but unexpectedly the mother did not carry the variant. Microsatellite repeat testing with markers covering chromosome 1 showed that the DPD deficiency in the child is due to paternal uniparental isodisomy. Our report thus extends the genetic spectrum underlying DPYD deficiency.

Genetic Mosaicism in Calmodulinopathy.

BACKGROUND: CaM (calmodulin) mutations are associated with congenital arrhythmia susceptibility (calmodulinopathy) and are most often de novo. In this report, we sought to broaden the genotype-phenotype spectrum of calmodulinopathies with 2 novel calmodulin mutations and to investigate mosaicism in 2 affected families. METHODS: CaM mutations were identified in 4 independent cases by DNA sequencing. Biochemical and electrophysiological studies were performed to determine functional consequences of each mutation. RESULTS: Genetic studies identified 2 novel CaM variants (CALM3-E141K in 2 cases; CALM1-E141V) and one previously reported CaM pathogenic variant (CALM3-D130G) among 4 probands with shared clinical features of prolonged QTc interval (range 505-725 ms) and documented ventricular arrhythmia. A fatal outcome occurred for 2 of the cases. The parents of all probands were asymptomatic with normal QTc duration. However, 2 of the families had multiple affected offspring or multiple occurrences of intrauterine fetal demise. The mother from the family with recurrent intrauterine fetal demise exhibited the CALM3-E141K mutant allele in 25% of next-generation sequencing reads indicating somatic mosaicism, whereas CALM3-D130G was present in 6% of captured molecules of the paternal DNA sample, also indicating mosaicism. Two novel mutations (E141K and E141V) impaired Ca2+ binding affinity to the C-domain of CaM. Human-induced pluripotent stem cell-derived cardiomyocytes overexpressing mutant or wild-type CaM showed that both mutants impaired Ca2+-dependent inactivation of L-type Ca2+ channels and prolonged action potential duration. CONCLUSIONS: We report 2 families with somatic mosaicism associated with arrhythmogenic calmodulinopathy, and demonstrate dysregulation of L-type Ca2+ channels by 2 novel CaM mutations affecting the same residue. Parental mosaicism should be suspected in families with unexplained fetal arrhythmia or fetal demise combined with a documented CaM mutation.

Expanding spectrum of human RYR2-related disease: new electrocardiographic, structural, and genetic features.

BACKGROUND: Catecholaminergic polymorphic ventricular tachycardia is a disease characterized by ventricular arrhythmias elicited exclusively under adrenergic stress. Additional features include baseline bradycardia and, in some patients, right ventricular fatty displacement. The clinical spectrum is expanded by the 2 families described here. METHODS AND RESULTS: Sixteen members from 2 separate families have been clinically evaluated and followed over the last 15 years. In addition to exercise-related ventricular arrhythmias, they showed abnormalities in sinoatrial node function, as well as atrioventricular nodal function, atrial fibrillation, and atrial standstill. Left ventricular dysfunction and dilatation was present in several affected individuals. Linkage analysis mapped the disease phenotype to a 4-cM region on chromosome 1q42-q43. Conventional polymerase chain reaction-based screening did not reveal a mutation in either the Ryanodine receptor 2 gene (RYR2) or ACTN2, the most plausible candidate genes in the region of interest. Multiplex ligation-dependent probe amplification and long-range polymerase chain reaction identified a genomic deletion that involved RYR2 exon-3, segregated in all the affected family members (n=16) in these 2 unlinked families. Further investigation revealed that the genomic deletion occurred in both families as a result of Alu repeat-mediated polymerase slippage. CONCLUSIONS: This is the first report on a large genomic deletion in RYR2, which leads to extended clinical phenotypes (eg, sinoatrial node and atrioventricular node dysfunction, atrial fibrillation, atrial standstill, and dilated cardiomyopathy). These features have not previously been linked to RYR2.

Human keratinocytes produce the complement inhibitor factor I: Synthesis is regulated by interferon-gamma.

Extrahepatic complement synthesis is believed to play an important role in host defense and inflammation at tissue and organ level. In the epidermis the most abundant cell type, keratinocytes have been shown to produce C3, factor B and factor H. In the present study, we investigated the synthesis of factor I by human keratinocytes. We also studied whether proinflammatory cytokines IL-1alpha, IL-6, TGF-beta1, TNF-alpha and IFN-gamma regulate factor I synthesis in keratinocytes. Human keratinocytes constitutively expressed factor I mRNA and produced factor I protein. Amongst the above-mentioned cytokines, only IFN-gamma regulated the synthesis of factor I, and this effect occurred predominantly at pre-translational level. Factor I produced by keratinocytes was functionally active in cleaving C3b. In conclusion, we demonstrate that keratinocytes are capable of synthesizing factor I, and that this synthesis is regulated by IFN-gamma.

Plakophilin-2 mutations are the major determinant of familial arrhythmogenic right ventricular dysplasia/cardiomyopathy.

BACKGROUND: Mutations in the plakophilin-2 gene (PKP2) have been found in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVC). Hence, genetic screening can potentially be a valuable tool in the diagnostic workup of patients with ARVC. METHODS AND RESULTS: To establish the prevalence and character of PKP2 mutations and to study potential differences in the associated phenotype, we evaluated 96 index patients, including 56 who fulfilled the published task force criteria. In addition, 114 family members from 34 of these 56 ARVC index patients were phenotyped. In 24 of these 56 ARVC patients (43%), 14 different (11 novel) PKP2 mutations were identified. Four different mutations were found more than once; haplotype analyses revealed identical haplotypes in the different mutation carriers, suggesting founder mutations. No specific genotype-phenotype correlations could be identified, except that negative T waves in V(2) and V(3) occurred more often in PKP2 mutation carriers (P<0.05). Of the 34 index patients whose family members were phenotyped, 23 familial cases were identified. PKP2 mutations were identified in 16 of these 23 ARVC index patients (70%) with familial ARVC. On the other hand, no PKP2 mutations at all were found in 11 probands without additional affected family members (P<0.001). CONCLUSIONS: PKP2 mutations can be identified in nearly half of the Dutch patients fulfilling the ARVC criteria. In familial ARVC, even the vast majority (70%) is caused by PKP2 mutations. However, nonfamilial ARVC is not related to PKP2. The high yield of mutational analysis in familial ARVC is unique in inherited cardiomyopathies.